The Smithsonian Institution occupies the former United States Patent Building, described by Walt Whitman as 'the noblest of Washington buildings'. Built between 1836 and 1867, the Patent Building is the finest example of Greek Revival architecture in the United States and a celebrated part of the capital's urban fabric. Now designated a National Historic Landmark, the building was rescued from demolition in 1958 by President Eisenhower, who transferred it to the Smithsonian to house the National Portrait Gallery and the Smithsonian American Art Museum. The enclosure of the building's grand central courtyard was prompted by a desire to transform the public's experience of the Smithsonian's galleries and create one of the largest event spaces in Washington.